1. Field of the Invention
Our invention pertains to the automatic positioning of work on machine tools. The invention is directed more specifically to a method of, and means for, automatically carrying or feeding work from a prescribed standby position to a machining position on a lathe of the type having a numerical control (N/C) system, sometimes called a "director" by the specialists, for automating its operation.
2. Description of the Prior Art
A variety of N/C machine tools which are equipped to automatically feed work to a machining position have been suggested and used. U.S. Pat. No. 3,691,879 issued to Blake on Aug. 19, 1972, for example, proposes a saddle-type turret lathe which features a gripper carried by a saddle-mounted turret for pulling a desired length of bar stock out of a chuck to a work station. An objection to this known work feed mechanism is its limited utility only in conjunction with continuous bar stock, not with discrete workpieces. Moreover, since the gripper is of the collet chuck type, with several resilient "fingers", it does not lend itself for use with bar stock of other than a preselected diameter.
Japanese Utility Model Laid Open Publication No. 33880/1975 and Japanese Patent Laid Open Publication No. 36683/1976 both teach the mounting of a work-gripping chuck, with movable jaws, on a turret for transporting and positioning cylindrical work on the chuck on the end of the work spindle. Such devices are objectionable in view of the inevitable limitations on the size of the work that can be held by the single work-gripping chuck on the turret. Further, the opening and closing of the chuck jaws requires complex control and actuating mechanisms.
Japanese Patent Publication No. 25992/1977 suggests a lathe in which a work gripper, also with movable jaws or fingers, is mounted in an indexing tailstock for pulling bar stock out of a hollow work spindle. The movable gripper jaws in the indexing tailstock are capable of handling not only continuous bar stock within the hollow work spindle but also other discrete, cylindrical workpieces. The sizes of the work that can be handled are also limited, however. Additional drawbacks are that the indexing tailstock with the built-in gripping means is extremely complex in construction and difficult to control, and that this concept does not apply, of course, to lathes having no tailstock.